Differential flotation of lead-zinc ores



lectively depressed.

It has been proposed to depress lead by the Patented Mar. 7, 1939 UNITED STATES PATENT OFFICE DIFFERENTIAL FL%TA]%ION OF LEAD-ZINC corporation of Maine No Drawing. Application November 6, 1937, Serial No. 173,112

10 Claims.

This invention relates to the differential flotation of ores containing lead and zinc and more particularly of ores containing lead, zinc and copper.

In the past ores containing lead and zinc or copper, lead and zinc have been floated by first floating 01f the copper and lead in the presence of a depressant for the zinc, such as sodium cyanide or zinc sulfate. The zinc is thenreacti- 10 vated and floated in a second zinc concentrate.

The separation as far as the zinc is concerned is not sufliciently complete because frequently zinc minerals are found in the ore which are very readily floatable and which are not adequately seaddition of chromic acid or sodium or potassium chromate. This results in a zinc concentrate of adequate grade but the recovery of the lead from the resulting tailings is not satisfactory as the lead is usually not suificiently concentrated.

The present invention is based'on the discovery -that if lead is .depressed with a chromate or bichromate and a zinc concentrate floated, it is 2 possible to reactivate the lead in the tailings and subject the tailings to a second flotation producing a lead concentrate of good grade, from which satisfactory recoveries of lead can be made. Preferably the flotation to produce the zinc is carried out in the presence of selective flotation agents which do not exhibit much collecting power for lead. An example of such reagents is ammonium disecondarybutyl dithiophosphate.

When'copper is present in a lead-zinc ore, the process of the invention is modified by first carrying out a selective copper flotation in the pres- ;ence of the bichromataand, if necessary, a zinc depressant, then activating the zinc and floating a zinc concentrate'and finally activating the lead 40 in the tailings-and obtaining a lead concentrate.

A number of lmaterials have been found to reactivate the lead sulfide. These include ferrous salts such 'as ferrous sulfate; hydrochloric acid; a

mixture of hydrochloric acid and sodium chlov 50 tails therein set forth. All of the flotations of the examples were carried out in Fagergren flotation machines.

EXAMPLE 1 A lead-zinc ore containing a mixture of galena 5 and sphalerite and having the following analysis:

Table I I ANALYSIS OF ORE was ground in a rod mill with 5.0 lbs/ton of potassium bichromate until about'59% of its weight would pass a ZOO-mesh sieve. The ore was then pulped to about 22% solids and 5 lbs/ton of copper sulfate (51-120) added and stirred with the pulp for six minutes before adding the promoter which consisted of 0.3 lbs/ton of ammonium disecondarybutyl dithiophosphat e and 0.05 lbs/ton of pine oil. The pulp was then floated to pro-. duce a zinc concentrate. The-tailing was then treated With 0.2 lbs/ton of potassium secondarybutyl xanthate and 0.05 lbs/ton of pine oil. A

second float was made to produce a lead concentrate. The metallurgical results of this example which was a control example without'activation of the tailing appears in Table II following Example 8.

EXAMPLE 2 produce a zinc concentrate. Then the tailings was activated with 5 lbs/ton of ferrous sulfate which was stirred in for four minutes before adding the xanthate and pine oil as described in 40 Example 1. After adding reagents, the ore was floated and a lead concentrate and tailing obtained. I

EXAMPLE 3 A zinc concentrate was produced as described in Example 1 and the tailing was activated with 5 lbs/ton ofpotassium ferro-cyanide instead of ferrous sulfate, as described in Example 2. The tailing was floated, after activation and addition of xanthate and frother, and a lead concentrate and tailing obtained.

. EXAMPLE 4 The ore was floated as described in Example 1 but instead of activating with 5 lbs/ton of ferrous sulfate, only 3 lbs/ton of this activator was used. The metallurgical results appear in the table and are substantially the same as with the larger quantity.

EXAMPLE 5 The ore was floatedto produce a zinc concentrate as described in Example 1 and then the tailing was activated with a mixture of 5 lbs/ton of sodium chloride and 6 lbs/ton of hydrochloric acid. After activation 0.2 lbs/ton of potassium secondarybutyl xanthate and 0.125 lbs/tonof pine oil were added. The lead concentrate was floated and the tailing obtained.

EXAMPLE 6 The ore was floated to produce a zinc concentrate as in Example 1 and then the tailing was activated with 5 lbs/ton of sodium hyposulfite. After activation 0.2 lbs/ton of potassium second arybutyl xanthate and 0.05 lbs/ton of pine oil were added and the material floated to produce a lead concentrate and lead tailing,

EXAMPLE '7 A zinc concentrate was produced as described in Example land the tailing then activated with 3 lbs/ton of sulfuric acid and promoter and frother added as in the preceding example. The material was floated to produce a lead concentrate and tailing.

ExAMPLE 8 The ore was floated to produce a zinc concentrate as described in Example 1 and the-tailing was then activated with 6 lbs/ton of hydrochloric acid. After activation 0.2 lbs/ton of potassium secondarybutyl xanthate and 0.2 lbs/ton of pine oil were added and the pulp floated to produce" a lead concentrate and tailing.

Table II METALLURGICAL RESULTS OF EXAMPLES l--8 (Feed assay approximately 32% lead, 28% zinc) Zinc concentrate Lead concentrate ample Grade Recoveries Grade Recoveries Pb Zn Pb Zn Pb Zn Pb 211 Tailing Overall recoveries Example No. Grade Recoveries Pb Zn Pb Zn Pb Zn From the examples it will be apparent that the lead recoveries are poor if no activation is used. According to the present invention, however, if activation is used the recoveries of lead are excellent. Potassium ferrocyanide while showing considerable activating power, was not as good as ferrous sulfate, hydrochloric acid, sulfuric acid or sodium hydrosulfite.

The examples describe the use of 'two typical flotation reagents for zinc and lead. In order to show the" comparative results of activation, the promoters were maintained constant throughout the tests on which the examples are based.- It

should be understood, however, that other reagents may be-. used, for example, in place of ammonium disecondarybutyl dithiophosphate, the corresponding sodium or potassium salt may be used, as Well as the salts of diethyl dithiophosphoric acid, diisopropyl dithi'ophosphoric acid or diamyl dithiophosphoric acid. The potassium secohdarybutyl xanthate may be replaced with other common lead reagents such as the sodium secondarybutyl xanthate, sodium or potassium isopropyl xanthate, sodium or potassium amyl xanthate and the like. The present invention is not limited to the use of a particular flotation promoter and includes in both the zinc and the lead float the use of any of the known promoters for these minerals.

EXAMPLE 9 A zinc-lead-copper ore having the following analysis: I

and-0.01 lb/ton of a mixture of mercaptobenzothiazole and sodium disecondary butyl dithiophosphate, together with 0.05 lbs/ton of a 50:50 mixture of sodium diethyl dithiophosphate and sodium disecondary butyl dithiophosphate werev 5663a together with 0.115 lbs/ton of a frother consisting of a mixturejpf aliphatic'alcohols of 710 carbon atoms with a saturated paraffin hydrocarbon. The pulp was floated to produce a.

copper concentrate. f

The tailing was activated by conditioning the pulp with4 lbs/ton of coppersulfate 511 20) for six minutes. To the conditioned pulp was then added 0.2 lbs/ton -of ammonium disecondary- ,butyl dithiophosphate and 0.046 .lbs/tonof the of potassium seoondarybutyl xanthate and 0.046 lbs/ton of pine oil. The pulp was then floated to produce a lead concentrate and a lead tailing;

The metallurgical results appear in the following table:

Table IV Copper concentrate Zine concentrate,

Assays percent Recoveries percent Assays percent on Pb' 'zn Cu Pb Zn Cu Pb Zn Recoveries percent Zinc concentrate, Lead concentrate Assays percent Recoveries percent 011' Pb Zn Cu Pb Zn Cu Pb Zn Tsilings Total overall, recoveries Assays percent Recoveries percent 7 With the exception of the lead activating agents, the reagent combinations used in Example 9 are typical flotation respectively. The invention of course is not limited to the useof these particular-reagents.

It will be understood that the grades of the concentrates in both Tables 11 and IV are not unduly high. The reason for this is that the concentrates shown in the tables represent rougher concentrates and the examples are intended to show the advantages .of the present invention in increasing the recovery of lead. Of course, in common; practice the rougher concentrates are cleaned to produce higher grade. Each concentrate is favorable for good grade and the tails returned to the head circuits in the usual way.

What we claim is:

'1. A method for the differential flotation of lead and zinc sulfide ores which comprises treatlead activator .is ferrous sulfate.

reagents for copper, lead and zinc cleaned separately under conditions takes place in the presence lead, floating the ore -with an amount of reagent insufficient to float the zinc but sumcient tofloat the copper to form a copper concentrate, activating the "zinc in the pulp with copper sulfate, subjecting the activated pulp to froth flotation in the presence of an amount of promoter suflicient to produce a zinc concentrate, activating the tailing by treatment with a compound selected from the group consisting of ferrous compounds, hydrochloric acid, sulfuric acid, hydrosulfltes and subjecting the activated tailing to froth flotation in the presence of flotation promoters capable of floating lead to produce a lead concentrate.

3. A method according to claim 1 in which the lead activator is ferrous sulfate.

4. A method according to claim 2 in which the 5. A method according to claim 1 in which the lead activator is hydrochloric acid.

6. A method according to claim 2 in which the lead activator is hydrochloric acid.

lead activator is sulfuric aci 8. A method according-to claim 2 in which the lead activator is sulfuric acid.

9. A method according to claim 1 in which the zinc flotation takes-place. in the presence of a dithiophosphate promoter andthe lead flotation takes place in the presence of a xanthate.

10.'A method accordingto claim 2 in which the copper flotation takes place in the presence of a very small amount of a dithiophosphate pro-- moter, the zinc flotation takes place in the presence of a larger amount and the lead flotation.

of a xanthate. ARVID EMIL ANDERSON. NORMAN HEDLEY. 

